Has any body had a problem with bending their exhaust valves on a WR400 with the exhaust cam timing set to YZ spec? I lost compressoion in my 99 WR and tore the top end appart to find out that one of the exhause valves is bent. I had it set to YZ spec and I'm wondering if this could be partly to blame. I think I probably over-reved it once or twice when I missed a gear so I think this also has something to do with the problem. Would this be less likely to happen again if I go back to stock WR spec? Any thoughts?